The only other place where I could have possibly screwed up the results is compilation. I had to build PHP from source, since I wanted to have the "latest greatest" and CentOS has dated packages at times. Though again, I remember just following the official instructions.

If you would like to have the test re-run, you'll have to harass some real FB engineers, since the test was performed on a devbox that I don't have access too anymore. You're also more then welcome to try it yourself and post some alternate benchmarks.

I think I can promise to link to your results from the blog post.